Which relates to the technical field of quantitative pumps, in particular to a differential quantitative pump, which comprises a PLC control device, a pressure fluid pipeline and a control device thereof, and comprises a pump body, a feeding end cover on the feed side of the pump body, A discharge side end cap on the material side, an active piston connected to the feed-side end cap in the pump body, a differential sleeve abutted on the active piston, a material feed port connected to the active piston and a discharge Mouth, connecting the feed-side end cap and the discharge side of the lateral cover connecting rod composed. The active piston is provided with two sealing rings. Differential sets have two seals inside and outside each ring. A lateral connecting rod passes through the differential sleeve and is connected to the driving piston by a bolt. The feed-side end cap and the discharge-side end cap are connected to the pump body by bolts. The active piston is connected with the electromagnetic pneumatic valve of the control device through the pipeline, and the electromagnetic pneumatic valve is connected with the PLC control device. Provide a small parts, simple mechanism, low failure rate, easy maintenance, low cost quantitative pump.